/*
 * Copyright (c) 2007-2012 Madhav Vaidyanathan
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 */


package com.midisheetmusic;

import java.io.*;
import java.lang.reflect.Array;
import java.util.*;
import android.util.*;

/** @class Pair - A pair of ints */
class PairInt {
    public int low;
    public int high;
}



/* MIDI file format.
 *Midi文件格式如下所述。 描述使用
 * The Midi File format is described below.  The description uses
 * the following abbreviations.
 *
 * u1     - One byte
 * u2     - Two bytes (big endian)
 * u4     - Four bytes (big endian)
 * 变体  可变长度整数，可以是1到4个字节。 的integer结束时，你遇到一个字节没有第8位设置(小于0x80的字节)
 * varlen - A variable length integer, that can be 1 to 4 bytes. The 
 *          integer ends when you encounter a byte that doesn't have 
 *          the 8th bit set (a byte less than 0x80).
 * 数据的长度取决于某些代码
 * len?   - The length of the data depends on some code
 *          
 *Midi文件以主Midi头文件开始
 * The Midi files begins with the main Midi header
 * u4 = The four ascii characters 'MThd'
 * u4 = The length of the MThd header = 6 bytes
 * u2 = 0 if the file contains a single track  如果文件包含单轨
 *      1 if the file contains one or more simultaneous tracks  单轨或者同声
 *      2 if the file contains one or more independent tracks  一个 或者 独立的轨道
 * u2 = number of tracks  轨道数量
 * u2 = if >  0, the number of pulses per quarter note  //每四分音符的脉冲数
 *      if <= 0, then ???
 *接下来是Midi的单曲
 * Next come the individual Midi tracks.  The total number of Midi
 * tracks was given above, in the MThd header.
 * 每一个轨道都开始于一个头文件
 *  Each track starts with a header:
 *
 * u4 = The four ascii characters 'MTrk'
 * u4 = Amount of track data, in bytes.  轨道数量
 * 一系列的midi事件
 * The track data consists of a series of Midi events.  Each Midi event
 * has the following format:
 *           the
 * varlen  - The time between the previous event and this event, measured
 *           in "pulses".  The number of pulses per quarter note is given
 *           in the MThd header.给出了每四分之一音符的脉冲数在MThd头中
 * u1      - The Event code, always betwee 0x80 and 0xFF
 * len?    - The event data.  The length of this data is determined by the
 *           event code.  The first byte of the event data is always < 0x80.
 *                  可选的
 * The event code is optional.  If the event code is missing, then it
 * defaults to the previous event code.  For example:
 *
 *   varlen, eventcode1, eventdata,
 *   varlen, eventcode2, eventdata,
 *   varlen, eventdata,  // eventcode is eventcode2
 *   varlen, eventdata,  // eventcode is eventcode2
 *   varlen, eventcode3, eventdata,
 *   ....
 *如何知道eventcode是否存在或丢失
 *   How do you know if the eventcode is there or missing? Well:
 *   - All event codes are between 0x80 and 0xFF  255
 *   - The first byte of eventdata is always less than 0x80.
 *   So, after the varlen delta time, if the next byte is between 0x80
 *   and 0xFF, its an event code.  Otherwise, its event data. 它是一个事件代码。 否则，它的事件数据。
 *
 * The Event codes and event data for each event code are shown below.
 *
 * Code:  u1 - 0x80 thru 0x8F - Note Off event.
 *             0x80 is for channel 1, 0x8F is for channel 16.
 * Data:  u1 - The note number, 0-127.  Middle C is 60 (0x3C)
 *        u1 - The note velocity.  This should be 0
 * 
 * Code:  u1 - 0x90 thru 0x9F - Note On event.
 *             0x90 is for channel 1, 0x9F is for channel 16.
 * Data:  u1 - The note number, 0-127.  Middle C is 60 (0x3C)
 *        u1 - The note velocity, from 0 (no sound) to 127 (loud).
 *             A value of 0 is equivalent to a Note Off. //等于0 相当于 关闭
 *
 * Code:  u1 - 0xA0 thru 0xAF - Key Pressure  压力值
 * Data:  u1 - The note number, 0-127.
 *        u1 - The pressure.
 *
 * Code:  u1 - 0xB0 thru 0xBF - Control Change //控制变换
 * Data:  u1 - The controller number
 *        u1 - The value
 *
 * Code:  u1 - 0xC0 thru 0xCF - Program Change  程序变换
 * Data:  u1 - The program number.
 *
 * Code:  u1 - 0xD0 thru 0xDF - Channel Pressure  频道压力
 *        u1 - The pressure.
 *
 * Code:  u1 - 0xE0 thru 0xEF - Pitch Bend  音高滑动
 * Data:  u2 - Some data
 *
 * Code:  u1     - 0xFF - Meta Event  重大事件
 * Data:  u1     - Metacode  元代码
 *        varlen - Length of meta event
 *        u1[varlen] - Meta event data.
 *
 *元事件代码如下:
 * The Meta Event codes are listed below:
 *
 * Metacode: u1         - 0x0  Sequence Number  音序器 编号
 *           varlen     - 0 or 2
 *           u1[varlen] - Sequence number
 *
 * Metacode: u1         - 0x1  Text
 *           varlen     - Length of text
 *           u1[varlen] - Text
 *
 * Metacode: u1         - 0x2  Copyright  版权
 *           varlen     - Length of text
 *           u1[varlen] - Text
 *
 * Metacode: u1         - 0x3  Track Name  轨道名字
 *           varlen     - Length of name
 *           u1[varlen] - Track Name
 *
 * Metacode: u1         - 0x58  Time Signature  时间签名
 *           varlen     - 4 
 *           u1         - numerator  计算者 计算器
 *           u1         - log2(denominator) 分母
 *           u1         - clocks in metronome click  节拍器计时器
 *           u1         - 32nd notes in quarter note (usually 8)
 *
 * Metacode: u1         - 0x59  Key Signature
 *           varlen     - 2
 *           u1         - if >= 0, then number of sharps  升半音
 *                        if < 0, then number of flats * -1  平
 *           u1         - 0 if major key  主要的
 *                        1 if minor key  少部分的
 *
 * Metacode: u1         - 0x51  Tempo 临时的
 *           varlen     - 3  
 *           u3         - quarter note length in microseconds  四分之一音符的长度，以微秒为单位
 */


/** @class MidiFile
 *
 * The MidiFile class contains the parsed data from the Midi File.
 * It contains:
 * midi文件中的所有曲目，包括每个曲目的所有MidiNotes
 * - All the tracks in the midi file, including all MidiNotes per track.
 * 时间签名(如4/ 4,3 / 4,6 /8)
 * The time signature (e.g. 4/4, 3/4, 6/8)
 * * -每四分音符的脉冲数。
 * - The number of pulses per quarter note.
 * * -节奏(每四分音符的微秒数)。
 * - The tempo (number of microseconds per quarter note).
 *包含来自MIDI文件的解析数据
 * The constructor takes a filename as input, and upon returning,
 * contains the parsed data from the midi file.
 *
 * The methods ReadTrack() and ReadMetaEvent() are helper functions called
 * 由构造函数解析
 * by the constructor during the parsing.
 *在解析和创建了MidiFile之后，用户可以检索
 * *通过使用属性tracks and tracks来跟踪和注释。 笔记
 * After the MidiFile is parsed and created, the user can retrieve the 
 * tracks and notes by using the property Tracks and Tracks.Notes.
 *有两种方法可以根据菜单修改midi数据
 * *选项选择:
 * There are two methods for modifying the midi data based on the menu
 * options selected:
 *
 * - ChangeMidiNotes()
 *   Apply the menu options to the parsed MidiFile.  This uses the helper functions:
 *     SplitTrack()支路
 *     CombineToTwoTracks()妥协
 *     ShiftTime()短时间
 *     Transpose()变换
 *     RoundStartTimes()
 *     RoundDurations()
 *
 * - ChangeSound()
 * 将菜单选项应用到MIDI音乐数据，并保存修改后的MIDI数据
 *   Apply the menu options to the MIDI music data, and save the modified midi data
 *   保存到文件中，以便回放
 *   to a file, for playback. 
 *   
 */

public class MidiFile {
    private static final String TAG = "MidiFileTAG";
    private FileUri fileuri;          /** The file reference 参考*/
    private String filename;          /** The Midi file name */
    private ArrayList<ArrayList<MidiEvent>> allevents; /** The raw MidiEvents, one list per track原始的midevents，每个曲目一个列表 */
    private ArrayList<MidiTrack> tracks ;  /** The tracks of the midifile that have notes 有音符的midfile音轨*/
    private short trackmode;         /** 0 (single单 track), 1 (simultaneous同声 tracks) 2 (independent单独 tracks) */
    private TimeSignature timesig;    /** The time signature 节拍*/
    private int quarternote;          /** The number of pulses per quarter note每四分音符的脉冲数 */
    private int totalpulses;          /** The total length of the song, in pulses 这首歌的总长度，用脉冲表示*/
    private boolean trackPerChannel;  /** True if we've split each channel into a track  如果我们把每个频道分成一个音轨，那就对了*/

    /* The list of Midi Events */
    public static final byte EventNoteOff         = (byte)0x80;
    public static final byte EventNoteOn          = (byte)0x90;
    public static final byte EventKeyPressure     = (byte)0xA0;
    public static final byte EventControlChange   = (byte)0xB0;  //控制改变
    public static final byte EventProgramChange   = (byte)0xC0;  //程序改变
    public static final byte EventChannelPressure = (byte)0xD0;  //评率压力
    public static final byte EventPitchBend       = (byte)0xE0;  //  音高的滑动
    public static final byte SysexEvent1          = (byte)0xF0;
    public static final byte SysexEvent2          = (byte)0xF7;
    public static final byte MetaEvent            = (byte)0xFF;

    /* The list of Meta Events */
    public static final byte MetaEventSequence      = (byte)0x0;  //序列顺序
    public static final byte MetaEventText          = (byte)0x1;  //
    public static final byte MetaEventCopyright     = (byte)0x2;  // 版权
    public static final byte MetaEventSequenceName  = (byte)0x3;  //序列名字
    public static final byte MetaEventInstrument    = (byte)0x4;  // 乐器
    public static final byte MetaEventLyric         = (byte)0x5;  // 歌词
    public static final byte MetaEventMarker        = (byte)0x6; //标记
    public static final byte MetaEventEndOfTrack    = (byte)0x2F;//音轨结束
    public static final byte MetaEventTempo         = (byte)0x51;//临时性的
    public static final byte MetaEventSMPTEOffset   = (byte)0x54;//单板滑雪
    public static final byte MetaEventTimeSignature = (byte)0x58;//拍子记号
    public static final byte MetaEventKeySignature  = (byte)0x59;//音调符号

    /* The Program Change event gives the instrument that should
     * be used for a particular channel.  The following table
     * maps each instrument number (0 thru 128) to an instrument
     * name.
     * 将每个仪器编号(0到128)映射到一个仪器
     *名字
     */
    public static String[] Instruments = {
        "Acoustic Grand Piano",   //声学钢琴
        "Bright Acoustic Piano",  //亮音大钢琴
        "Electric Grand Piano",  //电钢琴
        "Honky-tonk Piano",   //酒吧钢琴
        "Electric Piano 1",  //电钢琴
        "Electric Piano 2",//电钢琴
        "Harpsichord",//羽管键琴
        "Clavi",//古钢琴
        "Celesta",//钢片琴
        "Glockenspiel",//键盘式钟琴
        "Music Box",//音乐盒
        "Vibraphone",//电颤琴
        "Marimba",//木琴
        "Xylophone",//木琴
        "Tubular Bells",// 管钟
        "Dulcimer",//扬琴
        "Drawbar Organ",//爵士风琴
        "Percussive Organ",//打击式风琴
        "Rock Organ",//摇滚风琴
        "Church Organ",//教堂风琴
        "Reed Organ",//簧风琴
        "Accordion",//手风琴
        "Harmonica",//口琴
        "Tango Accordion",//探戈手风琴
        "Acoustic Guitar (nylon)",//原声吉他
        "Acoustic Guitar (steel)",//钢丝木吉他
        "Electric Guitar (jazz)",//电吉他 爵士
        "Electric Guitar (clean)",//电吉他(清音)
        "Electric Guitar (muted)",//闷音电吉他
        "Overdriven Guitar", //加驱动效果的电吉他
        "Distortion Guitar",//失真吉他
        "Guitar harmonics",//吉他和声
        "Acoustic Bass",//原声贝司
        "Electric Bass (finger)",//电贝斯(手指)
        "Electric Bass (pick)",//拨片电贝司
        "Fretless Bass",//无品贝司
        "Slap Bass 1",//重贝司
        "Slap Bass 2",
        "Synth Bass 1",//合成贝司
        "Synth Bass 2",
        "Violin",//小提琴
        "Viola",//中提琴
        "Cello",//大提琴
        "Contrabass",//低音大提琴
        "Tremolo Strings",//弦乐群颤音音色颤弓弦乐弦乐震音颤音弦乐
        "Pizzicato Strings",//弦乐群拨弦音色弦乐拨奏弹拨弦乐拨奏弦乐
        "Orchestral Harp",//竖琴弦乐乐队竖琴管弦乐的竖琴
        "Timpani",//定音鼓
        "String Ensemble 1",//弦乐合奏
        "String Ensemble 2",
        "SynthStrings 1",//合成弦乐
        "SynthStrings 2",
        "Choir Aahs",//人声合唱
        "Voice Oohs",//人声“嘟语音嗓音哦声合唱
        "Synth Voice",//轻声；低声；柔和的声音
        "Orchestra Hit",//管弦乐齐奏；打击交响乐
        "Trumpet",//小号
        "Trombone",// 长号
        "Tuba",//大号
        "Muted Trumpet",//弱音小号
        "French Horn",//法国号
        "Brass Section",//铜管乐；铜管乐合奏；铜管组；铜管乐组
        "SynthBrass 1",//管乐组合
        "SynthBrass 2",
        "Soprano Sax",//高音萨克斯风
        "Alto Sax",//高中音萨克斯声
        "Tenor Sax",//次中音萨克斯管；中音萨克斯风
        "Baritone Sax",//低音萨克斯管
        "Oboe",//双簧管
        "English Horn",//英国管
        "Bassoon",//低音管，巴松管
        "Clarinet",// 单簧管；竖笛
        "Piccolo",//短笛
        "Flute",//长笛
        "Recorder",//直笛
        "Pan Flute",//排萧
        "Blown Bottle",//吹瓶声
        "Shakuhachi",// 尺八（日本的一种5孔竹笛）
        "Whistle",//口哨声 汽笛
        "Ocarina",// 陶制的卵形笛
        "Lead 1 (square)",//平方 主奏
        "Lead 2 (sawtooth)",//锯齿
        "Lead 3 (calliope)",//蒸汽笛风琴
        "Lead 4 (chiff)",//雪纺主奏
        "Lead 5 (charang)",//沙朗主奏
        "Lead 6 (voice)",//声音引导
        "Lead 7 (fifths)",//五度音
        "Lead 8 (bass + lead)",
        "Pad 1 (new age)",//新世纪音乐
        "Pad 2 (warm)", //合成音垫
        "Pad 3 (polysynth)",//合成音垫合成器长音
        "Pad 4 (choir)",//人声合唱
        "Pad 5 (bowed)",//弓弦
        "Pad 6 (metallic)",//金属制的
        "Pad 7 (halo)",//光环
        "Pad 8 (sweep)",
        "FX 1 (rain)",//效果器  雨
        "FX 2 (soundtrack)",//原声音乐
        "FX 3 (crystal)",//晶体
        "FX 4 (atmosphere)",//大气
        "FX 5 (brightness)",//明亮
        "FX 6 (goblins)",//哥布林
        "FX 7 (echoes)",//回声
        "FX 8 (sci-fi)",//科幻
        "Sitar",//西塔琴
        "Banjo",//班卓琴
        "Shamisen",//三味线
        "Koto",//十三弦古筝
        "Kalimba",//克林巴琴
        "Bag pipe",// 风笛
        "Fiddle",//小提琴
        "Shanai",//乡村小提琴
        "Tinkle Bell",//叮当铃
        "Agogo",//拉丁打铃
        "Steel Drums",//钢鼓
        "Woodblock",//木鱼
        "Taiko Drum",//太鼓
        "Melodic Tom",//排鼓，古高音鼓
        "Synth Drum",//合成鼓
        "Reverse Cymbal",//反向铙钹
        "Guitar Fret Noise",//吉他换把杂音
        "Breath Noise",//呼吸的声音
        "Seashore",//海浪声
        "Bird Tweet",//鸟鸣
        "Telephone Ring",//手机
        "Helicopter",//直升飞机
        "Applause",//掌声
        "Gunshot",//射击
        "Percussion"//打击乐器(
    };
    /* End Instruments */

    /** Return a String representation of a Midi event */
    private String EventName(int ev) {
        if (ev >= EventNoteOff && ev < EventNoteOff + 16)
            return "NoteOff";
        else if (ev >= EventNoteOn && ev < EventNoteOn + 16) 
            return "NoteOn";
        else if (ev >= EventKeyPressure && ev < EventKeyPressure + 16) 
            return "KeyPressure";
        else if (ev >= EventControlChange && ev < EventControlChange + 16) 
            return "ControlChange";
        else if (ev >= EventProgramChange && ev < EventProgramChange + 16) 
            return "ProgramChange";
        else if (ev >= EventChannelPressure && ev < EventChannelPressure + 16)
            return "ChannelPressure";
        else if (ev >= EventPitchBend && ev < EventPitchBend + 16)
            return "PitchBend";
        else if (ev == MetaEvent)
            return "MetaEvent";
        else if (ev == SysexEvent1 || ev == SysexEvent2)
            return "SysexEvent";
        else
            return "Unknown";
    }

    /** Return a String representation of a meta-event */
    private String MetaName(int ev) {
        if (ev == MetaEventSequence)
            return "MetaEventSequence";
        else if (ev == MetaEventText)
            return "MetaEventText";
        else if (ev == MetaEventCopyright)
            return "MetaEventCopyright";
        else if (ev == MetaEventSequenceName)
            return "MetaEventSequenceName";
        else if (ev == MetaEventInstrument)
            return "MetaEventInstrument";
        else if (ev == MetaEventLyric)
            return "MetaEventLyric";
        else if (ev == MetaEventMarker)
            return "MetaEventMarker";
        else if (ev == MetaEventEndOfTrack)
            return "MetaEventEndOfTrack";
        else if (ev == MetaEventTempo)
            return "MetaEventTempo";
        else if (ev == MetaEventSMPTEOffset)
            return "MetaEventSMPTEOffset";
        else if (ev == MetaEventTimeSignature)
            return "MetaEventTimeSignature";
        else if (ev == MetaEventKeySignature)
            return "MetaEventKeySignature";
        else
            return "Unknown";
    }


    /** Get the list of tracks */
    public ArrayList<MidiTrack> getTracks() { return tracks; }

    /** Get the time signature */
    public TimeSignature getTime() { return timesig; }

    /** Get the file name */
    public String getFileName() { return filename; }

    /** Get the total length (in pulses) of the song */
    public int getTotalPulses() { return totalpulses; }


    /** Create a new MidiFile from the byte[] */
    public MidiFile(byte[] rawdata, String filename) {
        this.filename = filename;
        parse(rawdata);
    }

    /** Parse the given Midi file, and return an instance of this MidiFile
     * class.  After reading the midi file, this object will contain:
     * - The raw list of midi events
     * - The Time Signature of the song
     * - All the tracks in the song which contain notes. 
     * - The number, starttime, and duration of each note.
     * 解析给定的 Midi 文件，并返回此 MidiFile 类的实例。读取 MIDI 文件后，该对象将包含：
     * - MIDI 事件的原始列表 - 歌曲的时间签名 - 歌曲中包含音符的所有曲目。 - 每个音符的数量、开始时间和持续时间
     * 全局音轨还是含有音符的音轨，都以“4D 54 72 6B”开头
     * ASCII字符“MTrk 后跟着一个4个字节的整数，它标志了该轨道的字节数，这不包括前面的4个字节和本身的4个字节
     */
    private void parse(byte[] rawdata) {
        Log.i(TAG, "parse: " + Arrays.toString(rawdata));
        Log.i(TAG, "parse16: " + Utils.bytes2hex(rawdata));
        String id;
        int len;

        tracks = new ArrayList<MidiTrack>();
        trackPerChannel = false;

        MidiFileReader file = new MidiFileReader(rawdata);
        id = file.ReadAscii(4);
        if (!id.equals("MThd")) {
            throw new MidiFileException("Doesn't start with MThd", 0);
        }
        len = file.ReadInt(); 
        if (len !=  6) {
            throw new MidiFileException("Bad MThd header", 4);
        }
        trackmode = (short) file.ReadShort();
        int num_tracks = file.ReadShort();
        quarternote = file.ReadShort(); 

        allevents = new ArrayList<ArrayList<MidiEvent>>();
        for (int tracknum = 0; tracknum < num_tracks; tracknum++) {
            allevents.add(ReadTrack(file));
            MidiTrack track = new MidiTrack(allevents.get(tracknum), tracknum);
            if (track.getNotes().size() > 0) {
                tracks.add(track);
            }
        }

        /* Get the length of the song in pulses */
        for (MidiTrack track : tracks) {
            MidiNote last = track.getNotes().get( track.getNotes().size()-1 );
            if (this.totalpulses < last.getStartTime() + last.getDuration()) {
                this.totalpulses = last.getStartTime() + last.getDuration();
            }
        }

        /* If we only have one track with multiple channels, then treat
         * each channel as a separate track.
         */
        if (tracks.size() == 1 && HasMultipleChannels(tracks.get(0))) {
            tracks = SplitChannels(tracks.get(0), allevents.get(tracks.get(0).trackNumber() ));
            trackPerChannel = true;
        }

        CheckStartTimes(tracks);

        /* Determine the time signature */
        int tempoCount = 0;
        long tempo = 0;
        int numer = 0;
        int denom = 0;
        for (ArrayList<MidiEvent> list : allevents) {
            for (MidiEvent mevent : list) {
                if (mevent.Metaevent == MetaEventTempo) {
                    // Take average of all tempos
                    tempo += mevent.Tempo;
                    tempoCount++;
                }
                if (mevent.Metaevent == MetaEventTimeSignature && numer == 0) {
                    numer = mevent.Numerator;
                    denom = mevent.Denominator;
                }
            }
        }
        if (tempo == 0) {
            tempo = 500000; /* 500,000 microseconds = 0.05 sec */
        }
        else {
            tempo = tempo / tempoCount;
        }
        if (numer == 0) {
            numer = 4; denom = 4;
        }
        timesig = new TimeSignature(numer, denom, quarternote, (int)tempo);
    }

    /** Parse a single Midi track into a list of MidiEvents.
     * Entering this function, the file offset should be at the start of
     * the MTrk header.  Upon exiting, the file offset should be at the
     * start of the next MTrk header.
     */
    private ArrayList<MidiEvent> ReadTrack(MidiFileReader file) {
        ArrayList<MidiEvent> result = new ArrayList<MidiEvent>(20);
        int starttime = 0;
        String id = file.ReadAscii(4);

        if (!id.equals("MTrk")) {
            throw new MidiFileException("Bad MTrk header", file.GetOffset() - 4);
        }
        int tracklen = file.ReadInt();
        int trackend = tracklen + file.GetOffset();

        byte eventflag = 0;

        while (file.GetOffset() < trackend) {

            // If the midi file is truncated here, we can still recover.
            // Just return what we've parsed so far.

            int startoffset, deltatime;
            byte peekevent;
            try {
                startoffset = file.GetOffset();
                deltatime = file.ReadVarlen();
                starttime += deltatime;
                peekevent = file.Peek();
            }
            catch (MidiFileException e) {
                return result;
            }

            MidiEvent mevent = new MidiEvent();
            result.add(mevent);
            mevent.DeltaTime = deltatime;
            mevent.StartTime = starttime;

            // if (peekevent >= EventNoteOff) { 
            if (peekevent < 0) {
                mevent.HasEventflag = true; 
                eventflag = file.ReadByte();
            }

            //Log.e("debug",  "offset " + startoffset + 
            //                " event " + eventflag + " " + EventName(eventflag) +
            //                " start " + starttime + " delta " + mevent.DeltaTime);

            if (eventflag >= EventNoteOn && eventflag < EventNoteOn + 16) {
                mevent.EventFlag = EventNoteOn;
                mevent.Channel = ((byte)(eventflag - EventNoteOn));
                mevent.Notenumber = file.ReadByte();
                mevent.Velocity = file.ReadByte();
            }
            else if (eventflag >= EventNoteOff && eventflag < EventNoteOff + 16) {
                mevent.EventFlag = EventNoteOff;
                mevent.Channel = ((byte)(eventflag - EventNoteOff));
                mevent.Notenumber = file.ReadByte();
                mevent.Velocity = file.ReadByte();
            }
            else if (eventflag >= EventKeyPressure && 
                     eventflag < EventKeyPressure + 16) {
                mevent.EventFlag = EventKeyPressure;
                mevent.Channel = ((byte)(eventflag - EventKeyPressure));
                mevent.Notenumber = file.ReadByte();
                mevent.KeyPressure = file.ReadByte();
            }
            else if (eventflag >= EventControlChange && 
                     eventflag < EventControlChange + 16) {
                mevent.EventFlag = EventControlChange;
                mevent.Channel = ((byte)(eventflag - EventControlChange));
                mevent.ControlNum = file.ReadByte();
                mevent.ControlValue = file.ReadByte();
            }
            else if (eventflag >= EventProgramChange && 
                     eventflag < EventProgramChange + 16) {
                mevent.EventFlag = EventProgramChange;
                mevent.Channel = ((byte)(eventflag - EventProgramChange));
                mevent.Instrument = file.ReadByte();
            }
            else if (eventflag >= EventChannelPressure && 
                     eventflag < EventChannelPressure + 16) {
                mevent.EventFlag = EventChannelPressure;
                mevent.Channel = ((byte)(eventflag - EventChannelPressure));
                mevent.ChanPressure = file.ReadByte();
            }
            else if (eventflag >= EventPitchBend && 
                     eventflag < EventPitchBend + 16) {
                mevent.EventFlag = EventPitchBend;
                mevent.Channel = ((byte)(eventflag - EventPitchBend));
                mevent.PitchBend = (short) file.ReadShort();
            }
            else if (eventflag == SysexEvent1) {
                mevent.EventFlag = SysexEvent1;
                mevent.Metalength = file.ReadVarlen();
                mevent.Value = file.ReadBytes(mevent.Metalength);
            }
            else if (eventflag == SysexEvent2) {
                mevent.EventFlag = SysexEvent2;
                mevent.Metalength = file.ReadVarlen();
                mevent.Value = file.ReadBytes(mevent.Metalength);
            }
            else if (eventflag == MetaEvent) {
                mevent.EventFlag = MetaEvent;
                mevent.Metaevent = file.ReadByte();
                mevent.Metalength = file.ReadVarlen();
                mevent.Value = file.ReadBytes(mevent.Metalength);
                if (mevent.Metaevent == MetaEventTimeSignature) {
                    if (mevent.Metalength < 2) {
                        throw new MidiFileException(
                          "Meta Event Time Signature len == " + mevent.Metalength  + 
                          " != 4", file.GetOffset());
                    }
                    else {
                        mevent.Numerator = ((byte)mevent.Value[0]);
                        mevent.Denominator = ((byte)Math.pow(2, mevent.Value[1]));
                    }
                }
                else if (mevent.Metaevent == MetaEventTempo) {
                    if (mevent.Metalength != 3) {
                        throw new MidiFileException(
                          "Meta Event Tempo len == " + mevent.Metalength +
                          " != 3", file.GetOffset());
                    }
                    mevent.Tempo = ((mevent.Value[0] & 0xFF) << 16) | 
                                   ((mevent.Value[1] & 0xFF) << 8) | 
                                    (mevent.Value[2] & 0xFF);
                }
                else if (mevent.Metaevent == MetaEventEndOfTrack) {
                    /* break;  */
                }
            }
            else {
                throw new MidiFileException("Unknown event " + mevent.EventFlag,
                                             file.GetOffset()-1); 
            }
        }

        return result;
    }

    /** Return true if this track contains multiple channels.
     * If a MidiFile contains only one track, and it has multiple channels,
     * then we treat each channel as a separate track.
     */
    static boolean HasMultipleChannels(MidiTrack track) {
        int channel = track.getNotes().get(0).getChannel();
        for (MidiNote note : track.getNotes()) {
            if (note.getChannel() != channel) {
                return true;
            }
        }
        return false;
    }

    /** Write a variable length number to the buffer at the given offset.
     * Return the number of bytes written.
     */
    static int VarlenToBytes(int num, byte[] buf, int offset) {
        byte b1 = (byte) ((num >> 21) & 0x7F);
        byte b2 = (byte) ((num >> 14) & 0x7F);
        byte b3 = (byte) ((num >>  7) & 0x7F);
        byte b4 = (byte) (num & 0x7F);

        if (b1 > 0) {
            buf[offset]   = (byte)(b1 | 0x80);
            buf[offset+1] = (byte)(b2 | 0x80);
            buf[offset+2] = (byte)(b3 | 0x80);
            buf[offset+3] = b4;
            return 4;
        }
        else if (b2 > 0) {
            buf[offset]   = (byte)(b2 | 0x80);
            buf[offset+1] = (byte)(b3 | 0x80);
            buf[offset+2] = b4;
            return 3;
        }
        else if (b3 > 0) {
            buf[offset]   = (byte)(b3 | 0x80);
            buf[offset+1] = b4;
            return 2;
        }
        else {
            buf[offset] = b4;
            return 1;
        }
    }

    /** Write a 4-byte integer to data[offset : offset+4] */
    private static void IntToBytes(int value, byte[] data, int offset) {
        data[offset] = (byte)( (value >> 24) & 0xFF );
        data[offset+1] = (byte)( (value >> 16) & 0xFF );
        data[offset+2] = (byte)( (value >> 8) & 0xFF );
        data[offset+3] = (byte)( value & 0xFF );
    }

    /** Calculate the track length (in bytes) given a list of Midi events */
    private static int GetTrackLength(ArrayList<MidiEvent> events) {
        int len = 0;
        byte[] buf = new byte[1024];
        for (MidiEvent mevent : events) {
            len += VarlenToBytes(mevent.DeltaTime, buf, 0);
            len += 1;  /* for eventflag */
            switch (mevent.EventFlag) {
                case EventNoteOn: len += 2; break;
                case EventNoteOff: len += 2; break;
                case EventKeyPressure: len += 2; break;
                case EventControlChange: len += 2; break;
                case EventProgramChange: len += 1; break;
                case EventChannelPressure: len += 1; break;
                case EventPitchBend: len += 2; break;

                case SysexEvent1: 
                case SysexEvent2:
                    len += VarlenToBytes(mevent.Metalength, buf, 0); 
                    len += mevent.Metalength;
                    break;
                case MetaEvent: 
                    len += 1; 
                    len += VarlenToBytes(mevent.Metalength, buf, 0); 
                    len += mevent.Metalength;
                    break;
                default: break;
            }
        }
        return len;
    }


    /** Copy len bytes from src to dest, at the given offsets */
    private static void
    ArrayCopy(byte[] src, int srcoffset, byte[] dest, int destoffset, int len) {
        for (int i = 0; i < len; i++) {
            dest[destoffset + i] = src[srcoffset + i];
        }
    }

            
    /** Write the given list of Midi events to a stream/file.
     *  This method is used for sound playback, for creating new Midi files
     *  with the tempo, transpose, etc changed.
     *
     *  Return true on success, and false on error.
     */
    private static void
    WriteEvents(FileOutputStream file, ArrayList<ArrayList<MidiEvent>> allevents, 
                  int trackmode, int quarter) throws IOException {

        byte[] buf = new byte[16384];

        /* Write the MThd, len = 6, track mode, number tracks, quarter note */
        file.write("MThd".getBytes("US-ASCII"), 0, 4);
        IntToBytes(6, buf, 0);
        file.write(buf, 0, 4);
        buf[0] = (byte)(trackmode >> 8); 
        buf[1] = (byte)(trackmode & 0xFF);
        file.write(buf, 0, 2);
        buf[0] = 0; 
        buf[1] = (byte)allevents.size();
        file.write(buf, 0, 2);
        buf[0] = (byte)(quarter >> 8); 
        buf[1] = (byte)(quarter & 0xFF);
        file.write(buf, 0, 2);

        for (ArrayList<MidiEvent> list : allevents) {
            /* Write the MTrk header and track length */
            file.write("MTrk".getBytes("US-ASCII"), 0, 4);
            int len = GetTrackLength(list);
            IntToBytes(len, buf, 0);
            file.write(buf, 0, 4);

            for (MidiEvent mevent : list) {
                int varlen = VarlenToBytes(mevent.DeltaTime, buf, 0);
                file.write(buf, 0, varlen);

                if (mevent.EventFlag == SysexEvent1 ||
                    mevent.EventFlag == SysexEvent2 ||
                    mevent.EventFlag == MetaEvent) {
                    buf[0] = mevent.EventFlag;
                }
                else {
                    buf[0] = (byte)(mevent.EventFlag + mevent.Channel);
                }
                file.write(buf, 0, 1);

                if (mevent.EventFlag == EventNoteOn) {
                    buf[0] = mevent.Notenumber;
                    buf[1] = mevent.Velocity;
                    file.write(buf, 0, 2);
                }
                else if (mevent.EventFlag == EventNoteOff) {
                    buf[0] = mevent.Notenumber;
                    buf[1] = mevent.Velocity;
                    file.write(buf, 0, 2);
                }
                else if (mevent.EventFlag == EventKeyPressure) {
                    buf[0] = mevent.Notenumber;
                    buf[1] = mevent.KeyPressure;
                    file.write(buf, 0, 2);
                }
                else if (mevent.EventFlag == EventControlChange) {
                    buf[0] = mevent.ControlNum;
                    buf[1] = mevent.ControlValue;
                    file.write(buf, 0, 2);
                }
                else if (mevent.EventFlag == EventProgramChange) {
                    buf[0] = mevent.Instrument;
                    file.write(buf, 0, 1);
                }
                else if (mevent.EventFlag == EventChannelPressure) {
                    buf[0] = mevent.ChanPressure;
                    file.write(buf, 0, 1);
                }
                else if (mevent.EventFlag == EventPitchBend) {
                    buf[0] = (byte)(mevent.PitchBend >> 8);
                    buf[1] = (byte)(mevent.PitchBend & 0xFF);
                    file.write(buf, 0, 2);
                }
                else if (mevent.EventFlag == SysexEvent1) {
                    int offset = VarlenToBytes(mevent.Metalength, buf, 0);
                    ArrayCopy(mevent.Value, 0, buf, offset, mevent.Value.length);
                    file.write(buf, 0, offset + mevent.Value.length);
                }
                else if (mevent.EventFlag == SysexEvent2) {
                    int offset = VarlenToBytes(mevent.Metalength, buf, 0);
                    ArrayCopy(mevent.Value, 0, buf, offset, mevent.Value.length);
                    file.write(buf, 0, offset + mevent.Value.length);
                }
                else if (mevent.EventFlag == MetaEvent && mevent.Metaevent == MetaEventTempo) {
                    buf[0] = mevent.Metaevent;
                    buf[1] = 3;
                    buf[2] = (byte)((mevent.Tempo >> 16) & 0xFF);
                    buf[3] = (byte)((mevent.Tempo >> 8) & 0xFF);
                    buf[4] = (byte)(mevent.Tempo & 0xFF);
                    file.write(buf, 0, 5);
                }
                else if (mevent.EventFlag == MetaEvent) {
                    buf[0] = mevent.Metaevent;
                    int offset = VarlenToBytes(mevent.Metalength, buf, 1) + 1;
                    ArrayCopy(mevent.Value, 0, buf, offset, mevent.Value.length);
                    file.write(buf, 0, offset + mevent.Value.length);
                }
            }
        }
        file.close();
    }


    /** Clone the list of MidiEvents */
    private static ArrayList<ArrayList<MidiEvent>> 
    CloneMidiEvents(ArrayList<ArrayList<MidiEvent>> origlist) {
        ArrayList<ArrayList<MidiEvent>> newlist = 
           new ArrayList<ArrayList<MidiEvent>>(origlist.size());
        for (int tracknum = 0; tracknum < origlist.size(); tracknum++) {
            ArrayList<MidiEvent> origevents = origlist.get(tracknum);
            ArrayList<MidiEvent> newevents = new ArrayList<MidiEvent>(origevents.size());
            newlist.add(newevents);
            for (MidiEvent mevent : origevents) {
                newevents.add( mevent.Clone() );
            }
        }
        return newlist;
    }

    /** Create a new Midi tempo event, with the given tempo  */
    private static MidiEvent CreateTempoEvent(int tempo) {
        MidiEvent mevent = new MidiEvent();
        mevent.DeltaTime = 0;
        mevent.StartTime = 0;
        mevent.HasEventflag = true;
        mevent.EventFlag = MetaEvent;
        mevent.Metaevent = MetaEventTempo;
        mevent.Metalength = 3;
        mevent.Tempo = tempo;
        return mevent;
    }


    /** Search the events for a ControlChange event with the same
     *  channel and control number.  If a matching event is found,
     *  update the control value.  Else, add a new ControlChange event.
     */
    private static void
    UpdateControlChange(ArrayList<MidiEvent> newevents, MidiEvent changeEvent) {
        for (MidiEvent mevent : newevents) {
            if ((mevent.EventFlag == changeEvent.EventFlag) &&
                (mevent.Channel == changeEvent.Channel) &&
                (mevent.ControlNum == changeEvent.ControlNum)) {

                mevent.ControlValue = changeEvent.ControlValue;
                return;
            }
        }
        newevents.add(changeEvent);
    }


    /** Start the Midi music at the given pause time (in pulses).
     *  Remove any NoteOn/NoteOff events that occur before the pause time.
     *  For other events, change the delta-time to 0 if they occur
     *  before the pause time.  Return the modified Midi Events.
     */
    private static 
    ArrayList<ArrayList<MidiEvent>> StartAtPauseTime(ArrayList<ArrayList<MidiEvent>> list, int pauseTime) {
        ArrayList<ArrayList<MidiEvent>> newlist = new ArrayList<ArrayList<MidiEvent>>(list.size());
        for (int tracknum = 0; tracknum < list.size(); tracknum++) {
            ArrayList<MidiEvent> events = list.get(tracknum);
            ArrayList<MidiEvent> newevents = new ArrayList<MidiEvent>(events.size());
            newlist.add(newevents);

            boolean foundEventAfterPause = false;
            for (MidiEvent mevent : events) {

                if (mevent.StartTime < pauseTime) {
                    if (mevent.EventFlag == EventNoteOn ||
                        mevent.EventFlag == EventNoteOff) {

                        /* Skip NoteOn/NoteOff event */
                    }
                    else if (mevent.EventFlag == EventControlChange) {
                        mevent.DeltaTime = 0;
                        UpdateControlChange(newevents, mevent);
                    }
                    else {
                        mevent.DeltaTime = 0;
                        newevents.add(mevent);
                    }
                }
                else if (!foundEventAfterPause) {
                    mevent.DeltaTime = (mevent.StartTime - pauseTime);
                    newevents.add(mevent);
                    foundEventAfterPause = true;
                }
                else {
                    newevents.add(mevent);
                }
            }
        }
        return newlist;
    }

    /** Write this Midi file to the given file.
     * If options is not null, apply those options to the midi events
     * before performing the write.
     * Return true if the file was saved successfully, else false.
     */
    public void ChangeSound(FileOutputStream destfile, MidiOptions options)
      throws IOException {
        Write(destfile, options);
    }

    public void Write(FileOutputStream destfile, MidiOptions options) 
      throws IOException {
        ArrayList<ArrayList<MidiEvent>> newevents = allevents;
        if (options != null) {
            newevents = ApplyOptionsToEvents(options);
        }
        WriteEvents(destfile, newevents, trackmode, quarternote);
    }

    /** Apply the following sound options to the midi events:
     * - The tempo (the microseconds per pulse)
     * - The instruments per track
     * - The note number (transpose value)
     * - The tracks to include
     * Return the modified list of midi events.
     */
    public ArrayList<ArrayList<MidiEvent>>
    ApplyOptionsToEvents(MidiOptions options) {
        int i;
        if (trackPerChannel) {
            return ApplyOptionsPerChannel(options);
        }

        /* A midifile can contain tracks with notes and tracks without notes.
         * The options.tracks and options.instruments are for tracks with notes.
         * So the track numbers in 'options' may not match correctly if the
         * midi file has tracks without notes. Re-compute the instruments, and 
         * tracks to keep.
         */
        int num_tracks = allevents.size();
        int[] instruments = new int[num_tracks];
        boolean[] keeptracks = new boolean[num_tracks];
        for (i = 0; i < num_tracks; i++) {
            instruments[i] = 0;
            keeptracks[i] = true;
        }
        for (int tracknum = 0; tracknum < tracks.size(); tracknum++) {
            MidiTrack track = tracks.get(tracknum);
            int realtrack = track.trackNumber();
            instruments[realtrack] = options.instruments[tracknum];
            if (options.tracks[tracknum] == false || options.mute[tracknum] == true) {
                //每个声部 是否播放
                keeptracks[realtrack] = false;
            }
        }

        ArrayList<ArrayList<MidiEvent>> newevents = CloneMidiEvents(allevents);

        /* Set the tempo at the beginning of each track */
        for (int tracknum = 0; tracknum < newevents.size(); tracknum++) {
            MidiEvent mevent = CreateTempoEvent(options.tempo);
            newevents.get(tracknum).add(0, mevent);
        }

        /* Change the note number (transpose), instrument, and tempo */
        for (int tracknum = 0; tracknum < newevents.size(); tracknum++) {
            for (MidiEvent mevent : newevents.get(tracknum)) {
                int num = mevent.Notenumber + options.transpose;
                if (num < 0)
                    num = 0;
                if (num > 127)
                    num = 127;
                mevent.Notenumber = (byte)num;
                if (!options.useDefaultInstruments) {
                    mevent.Instrument = (byte)instruments[tracknum];
                }
                mevent.Tempo = options.tempo;
            }
        }

        if (options.pauseTime != 0) {
            newevents = StartAtPauseTime(newevents, options.pauseTime);
        }

        /* Change the tracks to include */
        int count = 0;
        for (int tracknum = 0; tracknum < keeptracks.length; tracknum++) {
            if (keeptracks[tracknum]) {
                count++;
            }
        }
        ArrayList<ArrayList<MidiEvent>> result = new ArrayList<ArrayList<MidiEvent>>(count);
        i = 0;
        for (int tracknum = 0; tracknum < keeptracks.length; tracknum++) {
            if (keeptracks[tracknum]) {
                result.add(newevents.get(tracknum));
                i++;
            }
        }
        return result;
    }


    /** Apply the following sound options to the midi events:
     * - The tempo (the microseconds per pulse)
     * - The instruments per track
     * - The note number (transpose value)
     * - The tracks to include
     * Return the modified list of midi events.
     *
     * This Midi file only has one actual track, but we've split that
     * into multiple fake tracks, one per channel, and displayed that
     * to the end-user.  So changing the instrument, and tracks to
     * include, is implemented differently than the ApplyOptionsToEvents() method:
     *
     * - We change the instrument based on the channel, not the track.
     * - We include/exclude channels, not tracks.
     * - We exclude a channel by setting the note volume/velocity to 0.
     */
    public ArrayList<ArrayList<MidiEvent>>
    ApplyOptionsPerChannel(MidiOptions options) {
        /* Determine which channels to include/exclude.
         * Also, determine the instruments for each channel.
         */
        int[] instruments = new int[16];
        boolean[] keepchannel = new boolean[16];
        for (int i = 0; i < 16; i++) {
            instruments[i] = 0;
            keepchannel[i] = true;
        }
        for (int tracknum = 0; tracknum < tracks.size(); tracknum++) {
            MidiTrack track = tracks.get(tracknum);
            int channel = track.getNotes().get(0).getChannel();
            instruments[channel] = options.instruments[tracknum];
            if (options.tracks[tracknum] == false || options.mute[tracknum] == true) {
                keepchannel[channel] = false;
            }
        }
        
        ArrayList<ArrayList<MidiEvent>> newevents = CloneMidiEvents(allevents);

        /* Set the tempo at the beginning of each track */
        for (int tracknum = 0; tracknum < newevents.size(); tracknum++) {
            MidiEvent mevent = CreateTempoEvent(options.tempo);
            newevents.get(tracknum).add(0, mevent);
        }

        /* Change the note number (transpose), instrument, and tempo */
        for (int tracknum = 0; tracknum < newevents.size(); tracknum++) {
            for (MidiEvent mevent : newevents.get(tracknum)) {
                int num = mevent.Notenumber + options.transpose;
                if (num < 0)
                    num = 0;
                if (num > 127)
                    num = 127;
                mevent.Notenumber = (byte)num;
                if (!keepchannel[mevent.Channel]) {
                    mevent.Velocity = 0;
                }
                if (!options.useDefaultInstruments) {
                    mevent.Instrument = (byte)instruments[mevent.Channel];
                }
                mevent.Tempo = options.tempo;
            }
        }
        if (options.pauseTime != 0) {
            newevents = StartAtPauseTime(newevents, options.pauseTime);
        }
        return newevents;
    }


    /** Apply the given sheet music options to the MidiNotes.
     *  Return the midi tracks with the changes applied.
     */
    public ArrayList<MidiTrack> ChangeMidiNotes(MidiOptions options) {
        ArrayList<MidiTrack> newtracks = new ArrayList<MidiTrack>();

        for (int track = 0; track < tracks.size(); track++) {
            if (options.tracks[track]) {
                newtracks.add(tracks.get(track).Clone() );
            }
        }

        /* To make the sheet music look nicer, we round the start times
         * so that notes close together appear as a single chord.  We
         * also extend the note durations, so that we have longer notes
         * and fewer rest symbols.
         */
        TimeSignature time = timesig;
        if (options.time != null) {
            time = options.time;
        }
        MidiFile.RoundStartTimes(newtracks, options.combineInterval, timesig);
        MidiFile.RoundDurations(newtracks, time.getQuarter());

        if (options.twoStaffs) {
            newtracks = MidiFile.CombineToTwoTracks(newtracks, timesig.getMeasure());
        }
        if (options.shifttime != 0) {
            MidiFile.ShiftTime(newtracks, options.shifttime);
        }
        if (options.transpose != 0) {
            MidiFile.Transpose(newtracks, options.transpose);
        }

        return newtracks;
    }


    /** Shift the starttime of the notes by the given amount.
     * This is used by the Shift Notes menu to shift notes left/right.
     */
    public static void
    ShiftTime(ArrayList<MidiTrack> tracks, int amount)
    {
        for (MidiTrack track : tracks) {
            for (MidiNote note : track.getNotes()) {
                note.setStartTime(note.getStartTime() + amount);
            }
        }
    }

    /** Shift the note keys up/down by the given amount */
    public static void
    Transpose(ArrayList<MidiTrack> tracks, int amount)
    {
        for (MidiTrack track : tracks) {
            for (MidiNote note : track.getNotes()) {
                note.setNumber(note.getNumber() + amount);
                if (note.getNumber() < 0) {
                    note.setNumber(0);
                }
            }
        }
    }

   
    /* Find the highest and lowest notes that overlap this interval (starttime to endtime).
     * This method is used by SplitTrack to determine which staff (top or bottom) a note
     * should go to.
     *
     * For more accurate SplitTrack() results, we limit the interval/duration of this note 
     * (and other notes) to one measure. We care only about high/low notes that are
     * reasonably close to this note.
     */
    private static void
    FindHighLowNotes(ArrayList<MidiNote> notes, int measurelen, int startindex, 
                     int starttime, int endtime, PairInt pair) {

        int i = startindex;
        if (starttime + measurelen < endtime) {
            endtime = starttime + measurelen;
        }

        while (i < notes.size() && notes.get(i).getStartTime() < endtime) {
            if (notes.get(i).getEndTime() < starttime) {
                i++;
                continue;
            }
            if (notes.get(i).getStartTime() + measurelen < starttime) {
                i++;
                continue;
            }
            if (pair.high < notes.get(i).getNumber()) {
                pair.high = notes.get(i).getNumber();
            }
            if (pair.low > notes.get(i).getNumber()) {
                pair.low = notes.get(i).getNumber();
            }
            i++;
        }
    }

    /* Find the highest and lowest notes that start at this exact start time */
    private static void
    FindExactHighLowNotes(ArrayList<MidiNote> notes, int startindex, int starttime,
                          PairInt pair) {

        int i = startindex;

        while (notes.get(i).getStartTime() < starttime) {
            i++;
        }

        while (i < notes.size() && notes.get(i).getStartTime() == starttime) {
            if (pair.high < notes.get(i).getNumber()) {
                pair.high = notes.get(i).getNumber();
            }
            if (pair.low > notes.get(i).getNumber()) {
                pair.low = notes.get(i).getNumber();
            }
            i++;
        }
    }


 
    /* Split the given MidiTrack into two tracks, top and bottom.
     * The highest notes will go into top, the lowest into bottom.
     * This function is used to split piano songs into left-hand (bottom)
     * and right-hand (top) tracks.
     */
    public static ArrayList<MidiTrack> SplitTrack(MidiTrack track, int measurelen) {
        ArrayList<MidiNote> notes = track.getNotes();
        int count = notes.size();

        MidiTrack top = new MidiTrack(1);
        MidiTrack bottom = new MidiTrack(2);
        ArrayList<MidiTrack> result = new ArrayList<MidiTrack>(2);
        result.add(top); result.add(bottom);

        if (count == 0)
            return result;

        int prevhigh  = 76; /* E5, top of treble staff */
        int prevlow   = 45; /* A3, bottom of bass staff */
        int startindex = 0;

        for (MidiNote note : notes) {
            int high, low, highExact, lowExact;
            
            int number = note.getNumber();
            high = low = highExact = lowExact = number;

            while (notes.get(startindex).getEndTime() < note.getStartTime()) {
                startindex++;
            }

            /* I've tried several algorithms for splitting a track in two,
             * and the one below seems to work the best:
             * - If this note is more than an octave from the high/low notes
             *   (that start exactly at this start time), choose the closest one.
             * - If this note is more than an octave from the high/low notes
             *   (in this note's time duration), choose the closest one.
             * - If the high and low notes (that start exactly at this starttime)
             *   are more than an octave apart, choose the closest note.
             * - If the high and low notes (that overlap this starttime)
             *   are more than an octave apart, choose the closest note.
             * - Else, look at the previous high/low notes that were more than an 
             *   octave apart.  Choose the closeset note.
             */
            PairInt pair = new PairInt();
            pair.high = high; pair.low = low;
            PairInt pairExact = new PairInt();
            pairExact.high = highExact; pairExact.low = lowExact;

            FindHighLowNotes(notes, measurelen, startindex, note.getStartTime(), note.getEndTime(), pair);
            FindExactHighLowNotes(notes, startindex, note.getStartTime(), pairExact);

            high = pair.high; low = pair.low;
            highExact = pairExact.high; lowExact = pairExact.low;

            if (highExact - number > 12 || number - lowExact > 12) {
                if (highExact - number <= number - lowExact) {
                    top.AddNote(note);
                }
                else {
                    bottom.AddNote(note);
                }
            } 
            else if (high - number > 12 || number - low > 12) {
                if (high - number <= number - low) {
                    top.AddNote(note);
                }
                else {
                    bottom.AddNote(note);
                }
            } 
            else if (highExact - lowExact > 12) {
                if (highExact - number <= number - lowExact) {
                    top.AddNote(note);
                }
                else {
                    bottom.AddNote(note);
                }
            }
            else if (high - low > 12) {
                if (high - number <= number - low) {
                    top.AddNote(note);
                }
                else {
                    bottom.AddNote(note);
                }
            }
            else {
                if (prevhigh - number <= number - prevlow) {
                    top.AddNote(note);
                }
                else {
                    bottom.AddNote(note);
                }
            }

            /* The prevhigh/prevlow are set to the last high/low
             * that are more than an octave apart.
             */
            if (high - low > 12) {
                prevhigh = high;
                prevlow = low;
            }
        }

        Collections.sort(top.getNotes(), track.getNotes().get(0) );
        Collections.sort(bottom.getNotes(), track.getNotes().get(0) );

        return result;
    }


    /** Combine the notes in the given tracks into a single MidiTrack. 
     *  The individual tracks are already sorted.  To merge them, we
     *  use a mergesort-like algorithm.
     */
    public static MidiTrack CombineToSingleTrack(ArrayList<MidiTrack> tracks)
    {
        /* Add all notes into one track */
        MidiTrack result = new MidiTrack(1);

        if (tracks.size() == 0) {
            return result;
        }
        else if (tracks.size() == 1) {
            MidiTrack track = tracks.get(0);
            for (MidiNote note : track.getNotes()) {
                result.AddNote(note);
            }
            return result;
        }

        int[] noteindex = new int[tracks.size() + 1];
        int[] notecount = new int[tracks.size() + 1];

        for (int tracknum = 0; tracknum < tracks.size(); tracknum++) {
            noteindex[tracknum] = 0;
            notecount[tracknum] = tracks.get(tracknum).getNotes().size();
        }
        MidiNote prevnote = null;
        while (true) {
            MidiNote lowestnote = null;
            int lowestTrack = -1;
            for (int tracknum = 0; tracknum < tracks.size(); tracknum++) {
                MidiTrack track = tracks.get(tracknum);
                if (noteindex[tracknum] >= notecount[tracknum]) {
                    continue;
                }
                MidiNote note = track.getNotes().get( noteindex[tracknum] );
                if (lowestnote == null) {
                    lowestnote = note;
                    lowestTrack = tracknum;
                }
                else if (note.getStartTime() < lowestnote.getStartTime()) {
                    lowestnote = note;
                    lowestTrack = tracknum;
                }
                else if (note.getStartTime() == lowestnote.getStartTime() && note.getNumber() < lowestnote.getNumber()) {
                    lowestnote = note;
                    lowestTrack = tracknum;
                }
            }
            if (lowestnote == null) {
                /* We've finished the merge */
                break;
            }
            noteindex[lowestTrack]++;
            if ((prevnote != null) && (prevnote.getStartTime() == lowestnote.getStartTime()) &&
                (prevnote.getNumber() == lowestnote.getNumber()) ) {

                /* Don't add duplicate notes, with the same start time and number */        
                if (lowestnote.getDuration() > prevnote.getDuration()) {
                    prevnote.setDuration(lowestnote.getDuration());
                }
            }
            else {
                result.AddNote(lowestnote);
                prevnote = lowestnote;
            }
        }
    
        return result;
    }


    /** Combine the notes in all the tracks given into two MidiTracks,
     * and return them.
     * 
     * This function is intended for piano songs, when we want to display
     * a left-hand track and a right-hand track.  The lower notes go into 
     * the left-hand track, and the higher notes go into the right hand 
     * track.
     */
    public static ArrayList<MidiTrack> CombineToTwoTracks(ArrayList<MidiTrack> tracks, int measurelen)
    {
        MidiTrack single = CombineToSingleTrack(tracks);
        ArrayList<MidiTrack> result = SplitTrack(single, measurelen);

        ArrayList<MidiEvent> lyrics = new ArrayList<MidiEvent>();
        for (MidiTrack track : tracks) {
            if (track.getLyrics() != null) {
                lyrics.addAll(track.getLyrics());
            }
        }
        if (lyrics.size() > 0) {
            Collections.sort(lyrics, lyrics.get(0));
            result.get(0).setLyrics(lyrics);
        }
        return result;
    }


    /** Check that the MidiNote start times are in increasing order.
     * This is for debugging purposes.
     */
    private static void CheckStartTimes(ArrayList<MidiTrack> tracks) {
        for (MidiTrack track : tracks) {
            int prevtime = -1;
            for (MidiNote note : track.getNotes()) {
                if (note.getStartTime() < prevtime) {
                    throw new MidiFileException("Internal parsing error", 0);
                }
                prevtime = note.getStartTime();
            }
        }
    }


    /** In Midi Files, time is measured in pulses.  Notes that have
     * pulse times that are close together (like within 10 pulses)
     * will sound like they're the same chord.  We want to draw
     * these notes as a single chord, it makes the sheet music much
     * easier to read.  We don't want to draw notes that are close
     * together as two separate chords.
     *
     * The SymbolSpacing class only aligns notes that have exactly the same
     * start times.  Notes with slightly different start times will
     * appear in separate vertical columns.  This isn't what we want.
     * We want to align notes with approximately the same start times.
     * So, this function is used to assign the same starttime for notes
     * that are close together (timewise).
     */
    public static void
    RoundStartTimes(ArrayList<MidiTrack> tracks, int millisec, TimeSignature time) {
        /* Get all the starttimes in all tracks, in sorted order */
        ListInt starttimes = new ListInt();
        for (MidiTrack track : tracks) {
            for (MidiNote note : track.getNotes()) {
                starttimes.add(note.getStartTime());
            }
        }
        starttimes.sort();

        /* Notes within "millisec" milliseconds apart will be combined. */
        int interval = time.getQuarter() * millisec * 1000 / time.getTempo();

        /* If two starttimes are within interval millisec, make them the same */
        for (int i = 0; i < starttimes.size() - 1; i++) {
            if (starttimes.get(i+1) - starttimes.get(i) <= interval) {
                starttimes.set(i+1, starttimes.get(i));
            }
        }

        CheckStartTimes(tracks);

        /* Adjust the note starttimes, so that it matches one of the starttimes values */
        for (MidiTrack track : tracks) {
            int i = 0;

            for (MidiNote note : track.getNotes()) {
                while (i < starttimes.size() &&
                       note.getStartTime() - interval > starttimes.get(i)) {
                    i++;
                }

                if (note.getStartTime() > starttimes.get(i) &&
                    note.getStartTime() - starttimes.get(i) <= interval) {

                    note.setStartTime(starttimes.get(i));
                }
            }
            Collections.sort(track.getNotes(), track.getNotes().get(0));
        }
    }


    /** We want note durations to span up to the next note in general.
     * The sheet music looks nicer that way.  In contrast, sheet music
     * with lots of 16th/32nd notes separated by small rests doesn't
     * look as nice.  Having nice looking sheet music is more important
     * than faithfully representing the Midi File data.
     *
     * Therefore, this function rounds the duration of MidiNotes up to
     * the next note where possible.
     */
    public static void
    RoundDurations(ArrayList<MidiTrack> tracks, int quarternote) {

        for (MidiTrack track : tracks ) {
            MidiNote prevNote = null;
            for (int i = 0; i < track.getNotes().size() - 1; i++) {
                MidiNote note1 = track.getNotes().get(i);
                if (prevNote == null) {
                    prevNote = note1;
                }

                /* Get the next note that has a different start time */
                MidiNote note2 = note1;
                for (int j = i+1; j < track.getNotes().size(); j++) {
                    note2 = track.getNotes().get(j);
                    if (note1.getStartTime() < note2.getStartTime()) {
                        break;
                    }
                }
                int maxduration = note2.getStartTime() - note1.getStartTime();

                int dur = 0;
                if (quarternote <= maxduration)
                    dur = quarternote;
                else if (quarternote/2 <= maxduration)
                    dur = quarternote/2;
                else if (quarternote/3 <= maxduration)
                    dur = quarternote/3;
                else if (quarternote/4 <= maxduration)
                    dur = quarternote/4;


                if (dur < note1.getDuration()) {
                    dur = note1.getDuration();
                }

                /* Special case: If the previous note's duration
                 * matches this note's duration, we can make a notepair.
                 * So don't expand the duration in that case.
                 */
                if ((prevNote.getStartTime() + prevNote.getDuration() == note1.getStartTime()) &&
                    (prevNote.getDuration() == note1.getDuration())) {


                    dur = note1.getDuration();
                }
                note1.setDuration(dur);
                if (track.getNotes().get(i+1).getStartTime() != note1.getStartTime()) {
                    prevNote = note1;
                }
            }
        }
    }

    /** Split the given track into multiple tracks, separating each
     * channel into a separate track.
     */
    private static ArrayList<MidiTrack> 
    SplitChannels(MidiTrack origtrack, ArrayList<MidiEvent> events) {

        /* Find the instrument used for each channel */
        int[] channelInstruments = new int[16];
        for (MidiEvent mevent : events) {
            if (mevent.EventFlag == EventProgramChange) {
                channelInstruments[mevent.Channel] = mevent.Instrument;
            }
        }
        channelInstruments[9] = 128; /* Channel 9 = Percussion */

        ArrayList<MidiTrack> result = new ArrayList<MidiTrack>();
        for (MidiNote note : origtrack.getNotes()) {
            boolean foundchannel = false;
            for (MidiTrack track : result) {
                if (note.getChannel() == track.getNotes().get(0).getChannel()) {
                    foundchannel = true;
                    track.AddNote(note); 
                }
            }
            if (!foundchannel) {
                MidiTrack track = new MidiTrack(result.size() + 1);
                track.AddNote(note);
                track.setInstrument(channelInstruments[note.getChannel()]);
                result.add(track);
            }
        }
        ArrayList<MidiEvent> lyrics = origtrack.getLyrics(); 
        if (lyrics != null) {
            for (MidiEvent lyricEvent : lyrics) {
                for (MidiTrack track : result) {
                    if (lyricEvent.Channel == track.getNotes().get(0).getChannel() ) {
                        track.AddLyric(lyricEvent);
                    }
                }
            }
        }
        return result;
    }


    /** Guess the measure length.  We assume that the measure
     * length must be between 0.5 seconds and 4 seconds.
     * Take all the note start times that fall between 0.5 and 
     * 4 seconds, and return the starttimes.
     */
    public ListInt
    GuessMeasureLength() {
        ListInt result = new ListInt();

        int pulses_per_second = (int) (1000000.0 / timesig.getTempo() * timesig.getQuarter());
        int minmeasure = pulses_per_second / 2;  /* The minimum measure length in pulses */
        int maxmeasure = pulses_per_second * 4;  /* The maximum measure length in pulses */

        /* Get the start time of the first note in the midi file. */
        int firstnote = timesig.getMeasure() * 5;
        for (MidiTrack track : tracks) {
            if (firstnote > track.getNotes().get(0).getStartTime()) {
                firstnote = track.getNotes().get(0).getStartTime();
            }
        }

        /* interval = 0.06 seconds, converted into pulses */
        int interval = timesig.getQuarter() * 60000 / timesig.getTempo();

        for (MidiTrack track : tracks) {
            int prevtime = 0;
            for (MidiNote note : track.getNotes()) {
                if (note.getStartTime() - prevtime <= interval)
                    continue;

                prevtime = note.getStartTime();

                int time_from_firstnote = note.getStartTime() - firstnote;

                /* Round the time down to a multiple of 4 */
                time_from_firstnote = time_from_firstnote / 4 * 4;
                if (time_from_firstnote < minmeasure)
                    continue;
                if (time_from_firstnote > maxmeasure)
                    break;

                if (!result.contains(time_from_firstnote)) {
                    result.add(time_from_firstnote);
                }
            }
        }
        result.sort();
        return result;
    }

    /** Return the last start time */
    public int EndTime() {
        int lastStart = 0;
        for (MidiTrack track : tracks) {
            if (track.getNotes().size() == 0) {
                continue;
            }
            int last = track.getNotes().get(track.getNotes().size()-1).getStartTime();
            lastStart = Math.max(last, lastStart);
        }
        return lastStart;
    }


    /** Return true if this midi file has lyrics */
    public boolean hasLyrics() {
        for (MidiTrack track : tracks) {
            if (track.getLyrics() != null) {
                return true;
            }
        }
        return false;
    }

    /** Return true if the data starts with the header MTrk */
    public static boolean hasMidiHeader(byte[] data) {
        String s;
        try {
            s = new String(data, 0, 4, "US-ASCII");
            if (s.equals("MThd"))
                return true;
            else
                return false;
        }
        catch (UnsupportedEncodingException e) {
            return false;
        }
    }


    @Override
    public String toString() {
        String result = "Midi File tracks=" + tracks.size() + " quarter=" + quarternote + "\n";
        result += timesig.toString() + "\n";
        for(MidiTrack track : tracks) {
            result += track.toString();
        }
        return result;
    }

    /* Command-line program to print out a parsed Midi file. Used for debugging.
     * To run:
     * - Change main2 to main
     * - javac MidiFile.java
     * - java MidiFile file.mid
     *
     */
    public static void main2(String[] args) {
        /**
        if (args.length == 0) {
            System.out.println("Usage: MidiFile <filename>");
            return;
        }
        String filename = args[0];
        byte[] data;
        try {
            File info = new File(filename);
            FileInputStream file = new FileInputStream(filename);

            data = new byte[ (int)info.length() ];
            int offset = 0;
            int len = (int)info.length();
            while (true) {
                if (offset == len)
                    break;
                int n = file.read(data, offset, len- offset);
                if (n <= 0)
                    break;
                offset += n;
            }
            file.close();
        }
        catch(IOException e) {
            return;
        }

        MidiFile f = new MidiFile(data, "");
        System.out.print(f.toString());
        **/
    }

}  /* End class MidiFile */



